As is well known, laminations made of sheets of ferrous material are employed in various electrical apparatus and provide a magnetic path. In transformers, the laminations provide a magnetic path around an electric current developed in a winding or other electrical conductor.
In some uses, as when the laminated assembly is employed as an electric sensor core in an overload relay and is required to respond linearly at low currents and continue a linear output throughout the desired current range while having an adequate high saturation level, the laminated assembly requires a large cross sectional area with minimal air gaps. Conventionally, this has been achieved through the use of laminations of relatively thin, sheets of ferrous material configured generally in the form of a "U" or a "D". The laminations are achieved by "U-U" or "D-U" laminations stacked in a sequence. This type of construction tends to require extra width on the ends of the laminations to compensate for the air gaps left between groups of laminations. Also typically, the laminations are riveted together or adhesively assembled using varnish or epoxy resin, or even held together with spring clips. If the extra width is not permitted because of spacial requirements of a given use, then two laminations are used per layer so as to minimize the air gap. However, as the extra width is eliminated and the assembly becomes narrower, it becomes increasingly difficult to utilize rivets to secure the laminations together. Moreover, as the assembly becomes thicker, spring clips lose their effectiveness and the use of varnish and/or epoxy as an adhesive tends to be messy and time consuming.
As a consequence, magnetic assemblies made up of laminations for use in transformers and the like have either been bulky, i.e. undesirably large, with a consequence that the volume of the equipment in which they are employed is increased or, if of an appropriate size matched to the requisite magnetic efficiency for the particular use, undesirably expensive to fabricate.
The present invention is directed to providing a compact magnetic assembly of the type that may be used in a transformer and which is economical to manufacture.